Potential impact and return period analysis study of Sumatra paleo megathrust earthquake using scaling law relations of earthquake parameter (case study: Siberut-West Sumatra megathrust earthquake 1797, Mw 8.2 ~ 8.8)

¹ Agency for Meteorology, Climatology and Geophysics, Jakarta, 10610, Indonesia
² Geophysical Station Padang Panjang, Indonesia
³ Department of Erath Sciences, Chiba University, Japan
⁴ Geological Engineering Department, Faculty of Engineering, Universitas Gadjah Mada, Yogyakarta 55281, Indonesia

^* Corresponding author: murjaya1@gmail.com

Abstract

The paleo-megathrust earthquake occurred in Siberut, West Sumatra in 1797 and it was estimated to have a magnitude (Mw) of about 8.2–8.8. This earthquake triggered a tsunami in the West Sumatra coast and its vicinity. The seismograph was not installed yet at that time, therefore it didn’t has earthquake parameter for advanced analysis. This study hoped to be able to see the earthquake potential impact if the earthquake occurred in this present era. Hereinafter using the scaling law relations of earthquake kinematic model in processing. The result is maximum intensity in Siberut and Tanahbala islands about VII-IX MMI, Painan, Padang, and Pariaman cities about V-VII MMI, and the northern part of West Sumatra region about VI-VII MMI. The PGA in Siberut and Tanahbala is about 60 % g, and Painan, Padang, and Pariaman are about 20 % g or more. Then the value of PGV in Siberut and Tanahbala is about 60 cm/s, in Painan about 10-20 cm/s, and in Padang and Pariaman city about 20-30 cm/s. Furthermore, an estimation of the return period of the earthquake if the source mechanism was modelled as a thrust and strike-slip faults for Mw 8.2-8.8 about 185 until 235 years and 336 until 616 years respectively.